The role of arachidonic acid (AA) metabolites in both normal and abnormal development is an unexplored area of biology. There is much circumstantial and increasing amounts of direct evidence that AA metabolites play a role in normal development and that interference with AA metabolism with anti-inflammatory drugs is teratogenic. In the proposed studies, the identity of a rare and unusual lipoxygenase product, 9-HETE, synthesized in substantial amounts by d. 12 rat embryos in vitro, will be confirmed using GC-MS. We have shown that a unique cytotoxic (and subsequently teratogenic) effect of aspirin can be prevented by concomitant administration of lipoxygenase inhibitors. The biochemistry of this interaction will be explored by measuring lipoxygenase product synthesis in untreated embryonic tissue, embryo tissue incubated with anti-inflammatory drugs (aspirin, sodium salicylate, indomethacin, others), tissue incubated with either of three lipoxygenase inhibitors, and tissue incubated with anti-inflammatory drugs plus lipoxygenase inhibitors. A similar set of experiments will be done on embryos exposed to the various drugs in utero during the teratogenic period of aspirin. Lipoxygenase product synthesis will be quantitated using thin layer chromatography/autoradiography and high pressure liquid chromatography. We predict that embryonic tissue will synthesize large amounts of a lipoxygenase product, whose synthesis will be enhanced by exposure to aspirin (the presumed cytotoxic/teratogenic insult) in vitro and in utero, and that this enhanced synthesis can be blocked by concomitant treatment with lipoxygenase inhibitors. Prostaglandin synthesis by the embryonic kidney anlagen, the uteric bud and metanephric blastema will be further documented. The effect of various arachidonic acid metabolites on nephrogenesis in vitro will be investigated. And finally, the development of blood supply and the role of prostaglandins as angiogenic factors will be examined in vitro using histologic and immunofluorescent techniques.